The bone mineral measurement core is necessary for the measurement of bone mass in both humans and in animals. The core has served the past two SCOR applications and has proven to be a cost effective mechanism of providing high precision measurements for 4 of the 5 projects proposed in this application. In Project 1, the vertebrae and femur of 24 transgenic mice will be measured in year 4. This core will be used to evaluate bone mass changes in mice and the excised bones from rats. In vivo measurements of L4-L6 vertebrae and the femur will be made 3 times per year in 80 live mice per year over the course of the experiment. Ex vivo samples of the femur and vertebrae in 65 rats each year will be measured by utilizing the DXA. Total sample measurements per year will be 580 scans. In Project 4, the cohort of 89 women with primary hyperparathyroidism will have bone mineral measurements at 3 skeletal sites (spine, hip, forearm) every 12 months to determine longitudinal changes in bone mass with medical treatment and following parathyroidectomy (total number of scans is 1068).This core will be used to compare the bone density response to hPTH 1-34 in estrogen deficient women, women on estrogen therapy and women in estrogen and placebo control groups. The bone density response to discontinuation and a later rechallenge of hPTH 1-34 will also be measured. Project 6 involves serial bone density measures (duplicate scans at baseline and every 6 months) at 5 skeletal sites (lumbar spine, hip, forearm, total body, and lateral spine) during the treatment, its' withdrawal and a later rechallenge. The total number of scans for all protocols in Project 6 is 4900. We have also incorporated into the core a feasibility study to determine whether micro-MRI can provide information equivalent to conventional histomorphometry and further improve the ability of bone mass to predict bone strength in the animal model. In addition to providing core support for the individual projects in this grant, the core has also been integral to the success of other NIH funded studies, at no additional cost to the SCOR grant.